Actually we don’t set-up a backlink, we do link-building or back link submission as a part of SEO strategy.
There are certain ways of building high quality links, and you can also do this without guest posting. Your best bet is to find resources pages related to your field and track the comments.
Yes - but most of those are out-of-date and/or misleading and inaccurate. They ignore the fact that PageRank is calculated per page, not per site. So while the home page may have high PR, inner pages where you may place a link are likely to have very low PR.
Also, Google places very little value on links which you place yourself, and recommends webmasters mark all such links nofollow.